You can also set constraints to VALIDATE or NOVALIDATE, in any combination with ENABLE or DISABLE, where: ENABLE ensures that all incoming data conforms to the constraint DISABLE allows incoming data, regardless of whether it conforms to the constraint VALIDATE ensures that existing data conforms to the constraint NOVALIDATE means that some existing data may not conform to the constraint In addition: - ENABLE VALIDATE is the same as ENABLE.
The constraint is checked and is guaranteed to hold for all rows.
CHECK constraints are simply conditional statements (predicates that return TRUE or FALSE) that refer to table columns for maintaining data integrity.
When one inserts data into a column or several columns in a single row, CHECK constraints come into action. In case the data does not meet the condition specified in the CHECK constraint, the insertion fails.
We will see how to add CHECK constraints to SQL Server table columns and discuss the pitfalls you may encounter when using this type of SQL Server constraints.I often ask those to find the mistake in this script when they claim to know the syntax very well.Have you ever disabled and enabled constraints in your production environment? Reference: Pinal Dave (https://blog.sqlauthority.com)Pinal Dave is a SQL Server Performance Tuning Expert and an independent consultant.The database level validation is necessary, but not sufficient for building effective and usable systems.Of course, when you are updating data external to your organization (say placing an order over web service), then clearly the handling of errors raised by the web service must be handled in an application.